Shock absorber for pumps



1966 c. s. ROBINSON 3,288,455

SHOCK ABSORBER FOR PUMPS Filed Dec. 29, 1964 2 SheetsSheet l Nov. 29, 1966 c. s. ROBINSON SHOCK ABSORBER FOR PUMPS 2 Sheets-Sheet 2 Filed Dec. 29, 1964 United States Patent 3,288,455 SHOCK ABSORBER FOR PUMPS Cecil S. Robinson, Englewood, N.J., assignor to Robinson Technical Products, Inc., Teterboro, N.J., a corporation of New York Filed Dec. 29, 1964, Ser. No. 421,823 14 Claims. (Cl. 267-1) This invention relates to shock-absorbers and more particularly to combined coupling and shock-absorbing devices adapted to be inserted between pumping mechanisms and reciprocatory pump rods or strings of the types widely used in connection with wells of great depth. The invention will be illustrated and described in a typical form adapted for use with a pumping rig and sucker rod string typical of those used in the pumping of oil wells and the adaptability of the invention to use with other types of oil-well, water-well or similar pumping arrangements will be apparent.

The present invention provides for the use of combined cushioning and damping devices comprising coil springs and resilient metal cushions which together transmit the force required to lift the sucker rod string and the oil or other liquid being pumped and which yield to abso-rb and smooth out the shock incident to application of lifting force to the rod string without rebound effect. The metal cushions which have a very high damping factor serve to minimize such rebound and furthermore they absorb, dissipate and clamp the high frequency shock pulses, which frequently exceed normal lift loads. The shock pulses are caused, among other things, by uneven liquid flow and changes in friction effect between the rod string and the well casing. It is such relatively high frequency shock pulses which normally result in failure due to fatigue and crystallization of the rod string and to similar deterioration or wear and tear of working elements of the pumping rig. Use of the present invention has increased by several times the periods between shutdown of oil-well pumping operations due to rod string breakage and/ or pumping rig failure.

The present invention provides such combined coil spring and metal cushion shock absorbers in a unit of such construction and geometry as to afford convenient and rapid assembly and disassembly with the rod string and pumping rig and to afford pumping operations in which substantially no lateral stresses are applied by the pumping mechanism to the rod string. The advantages relating to assembly and disassembly are achieved by providing rugged but light weight devices which are secured to the bridle cable including cup-shaped members into which the cable ends may be secured and these cup-shaped members preferably are separable from the other cable attaching devices whereby the babbitting of the cable ends into the cup-shaped members may be performed without any danger of heat damage or fouling of the other devices. The heavy parts of the shock absorber may be placed upon the polish rod and are so designed that the cable attaching devices upon the cab-1e ends may be quickly attached or removed. The geometry by which the application of lateral bending stresses to the rod-string (actually to the uppermost rod on the string which is called a polish rod) is avoided is of particular importance. Essentially it is achieved by positioning one or more spring means such as coil spring and metal cushion combinations concentrically with or in generally symmetrical arrangement with respect to the axis of the polish rods and providing a rigid support for the lower ends of such combinations to which the lifting force is applied. A rigid upper plate, separate from the lower support, rests upon the upper ends of such combinations and serves to support the polish rod with the attached level of the pump cylinder.

rod string. Since the coil spring and cushion combinations are capable of deflection in lateral as well as vertical directions they could tilt and thus apply lateral and bending stress upon the polish rod if the bridle cables were merely secured to the lower support plate and were free to flex laterally at any point between the lower and upper support plates. However, this is avoided by providing, in effect, rigid continuations of the lower support plate which extends upwardly at least to approximately the horizontal plane in which the polish rod is supported by the upper plate. The bridle cable ends are, in effect, passed through such continuations and thus are prevented from flexing in the critical locations.

It is in an object of the present invention to provide a shock absorbing device having the features and advantages outlined above. Other and further objects, features and advantages will become apparent from the following detailed description of a preferred, but not necessarily the only, embodiment of the invention, taken in connection with the drawings forming a part of this specification.

In the drawings:

FIG. 1 is a plan view of a shock absorber embodying the present invention, with certain parts in section and with certain parts shown in a dotted line position as well as in a solid line position;

FIG. 2 is a vertical sectional view taken along the irregular line 2-2 in FIG. 1;

FIG. 3 is a fragmentary horizontal sectional view taken along the line 33 in FIG. 2; and

FIG. 4 is vertical sectional view of the attaching parts illustrating a way in which such parts may be assembled with a bridle cable preparatory to the installation of the shock absorber of the present invention at a well.

Referring now to the drawings a shock-absorber embodying the present invention is generally indicated by the reference numeral 10. In FIGS. 1 and 2, in solid lines, it is shown suspended upon the lower end portions 12 and 14 of a bridle cable the upper portion of which, in a typical installation, will be secured to a horsehead or equivalent portion of a pumping rig (not shown). The uppermost rod of a pump-rod string, called a polish (or polished) rod, is indicated at 16. The rod 16 extends downwardly through suitable packing at the well head (not shown) and is coupled with the string of pump rods which extend within the well casing (not shown) to the Such rod strings may be from several hundred to several thousand feet long. The weight of the pump rod string plus the weight of the column of liquid being pumped is quite large, for example a lifting force of about 20,000 pounds is required for v pumping an oil well approximately 8000 feet deep.

The polish rod 16 has secured thereto a polish-rod clamp 18 which may be of any construction suitable for fimnly gripping the rod '16 in order that lifting of the clamp 18 will be effective to lift the rod 16 and attached pumprod string in the pumping operation. The clamp .18 chosen for illustration includes a body 20 which is bifurcated and surrounds the rod 16, being held in gripping relation therewith by nuts and bolts 23, 25.

The shock absorber 10, of the present invention, is designed to be interposed between the bridle cable 12, 14 and the polish rod clamp 18 to absorb and isolate shock and vibratory loads which otherwise would be transmitted between the pumping rig and the rod string. It will be understood that the polish rod 16 and bridle cable 12, 14 ordinarily will be at the well site installed and ready for use at a new well or installed and coupled together by known devices at an operating well. The polish rod as well as the bridle cable may have any one of several diameters customarily used. The shock absorber 10 of the present invention is intended to be shipped to the well site in such assembled or partially assemble-d condition and where required with such a variety of adapters for different polish rod and bridle cable sizes as to permit rapid and convenient installation without the need for any equipment or tools other than what is customarily used and readily available at a well site.

The shock absorber comprises a rigid base member (FIG. 2) and a rigid load-supporting member 22. The members 20 and 22 may be high-strength metal castings or forgings or they may be built up from appnopriately machined components as desired. The base member 20 is provided with a central opening 24 through which the polish rod 16 may freely extend and a plurality of shallow circular recesses 26 in the upper surface thereof. The recesses 26 each serve to receive and retain against lateral movement the lower end of a helical spring 28. As shown particularly in FIG. 1 there are four recesses 26 and four springs 28. The upper end of each spring 28 is received in a shallow circular recess 30 provided in the lower surface of the load-supporting member 22. In each spring 28 there is positioned a yieldable metal cushion 32 which will be described in greater detail hereinbelow. The metal cushions 32 extend the full length of the springs 28 and serve with the springs to yieldably support the load-supporting member 22 with respect to the base member 20.

While four spring and cushion combinations 28, 32 are shown herein and while the central vertical axes of the springs are shown spaced equidistantly from the central vertical axis of the polish rod 16 it will be understood that other numbers of springs and cushions may be used. For example, for use with shallow wells a single spring, with or without a cushion provided with a central opening, may be positioned concentrically with the rod 16. The spacing and arrangement of two or more springs, cushions or combinations thereof relative to the polish rod needs only to be sufiiciently symmetrical to minimize .any tendency of the load-supporting member 22 to tilt relative to the base member 20 under the operating conditions for which the shock absorber 10 is designed.

As shown most clearly in FIGS. 2 and 3 the rigid base member 20 is provided with hollow, upwardly-extending, frusto-conical formations 34 and 36 the interiors of which open into the side walls of the base member 20 as indicated at 38 and 40. Beneath the formations 34 and 36 there are formed in the base member 20 recesses 42 and 44 which are circular in cross-section and have the axes thereof in alignment with the axis of the central opening 24. In the assembled, operative position illustrated in full lines in FIG. 2 the recesses 42 and 44 receive cupshaped members 46 and 48, respectively, which are secured to the lower ends of the bridle cable 12, 14.

The upper surfaces of the cup-shaped members 46 and 48 bear respectively on the lower ends of tubular cable guides 50 and 52 which extend upwardly through the hollow formations 34 and 36 and terminate at their upper ends in a plane which is generally coincident with the plane of the upper surface of the load supporting member 22. The lower ends of the tubular cable guides 50 and 52 have secured thereto, as by welding, flanges 54 and 56 which are of such diameter as to rest against the upper surfaces of the recesses 42 and 44 so that upon lifting of the bridle cable 12, 14 the cups 46 and 48 Will bear upon the flanges 54 and 56 as well as upon the cable guides 50 and 52 to transmit the lifting effort to the base member 20.

The cable guides 50 and 52 have external threaded portions 58 and 60 in the vicinity of the upper ends of the formations 34 and 36. These threaded portions are adapted to receive clamp nuts 62 and 64 which have flaring skirts designed to telescope over the upper ends of the formations 34 and 36. As will be apparent the clamp nuts 62 and 64 are intended to be screwed down tightly over the upper ends of the formations 34 and 36 thereby rigidly securing the cups 46 and 48 within the recesses 42 and 44 of the base 20 and rigidly securing the tubular cable guides with respect to the base 20. Thus, in effect the tubular cable guides serve as rigid vertical extensions of the base 20. Since such extensions (the cable guides 50 and 52) terminate, as noted above, generally in the plane of the upper surface of the load supporting member 22 and since the bridle cable 12, 14 emerges from the upper ends of the cable guides it will be apparent that the cable is prevented from flexing at any point below the points of emergence from the guides. Thus the cable 12, 14 is free to flex only above the general plane in which the load is carried by the shock-absorber of the present invention. By this construction tilting, with attendant lateral bending stress upon the polish rod 16 is effectively minimized.

A particular feature of the present invention is the provision of a structure having the non-tilting advantages just referred to and which may be rapidly and conveniently assembled with a bridle cable and polish rod at a well site and disconnected with equal convenience when .the well requires maintenance. To this end the formations 34 and 36 and the side walls of the base member 20 are provided with the openings 38 and 40, referred to above. These openings have a width only somewhat greater than the outside diameter of the tubular cable guides 50 and 52 whereby when the cable guides and the cups 46 and 48 have been assembled on the ends of the bridle cable 12, 14 and the clamp nuts 62 and 64 have been backed off, upwardly, into the positions shown in dotted lines in FIGS. 2 and 3, the assemblies on the cable ends may be inserted through the openings 38, 40 and brought into positions for securing to the base member 20.

The upper, load-supporting member 22 is provided with openings 66 and 68 which are in vertical alignment with the openings 38 and 40 in the base 20. However, the openings 66 and 68 are considerably wider and deeper than the openings in the base to give ample clearance for the extension therethrough of the upper ends of the cable guides 50 and 52. Thus, the assemblies of cable guides and cups on the bridle cable ends may be readily inserted from the sides of the-shock absorber of the present invention whereupon the clamp nuts 62 and 64 may be screwed down over the upper ends of the formations 34 and 36 to complete the assembly of the shock absorber.

Preferably, the cable guides 50 and 52 are also provided with lock nuts 70 and 72 which may be brought down into locking engagement with the upper surfaces of the clamp nuts 62 and 64 to hold the latter in place. Preferably, also, the hexagonal or other shapes on the clamp nuts and lock nuts aforesaid are large in size whereby they may be engaged by the large heavy'duty wrenches normally available at a well site and the need for special or small-size tools is obviated. This is of advantage in the initial assembly as well as in subsequent disassembly and reassembly incident to well maintenance.

Referring now to FIG. 4 there is illustrated a manner in which certain of the detachable parts of the shock absorber of the present invention may be assembled with the bridle cable. The bridle cable is removed from the horse-head and is cut to suitable length so that the portions 12, 14 thereof will terminate at desired level with respect to the well head. The cable then may be laid upon the ground or other surface. The lock nut 70 and the clamp nut 62 are strung upon the cable portion 14 separately, as illustrated, or they may be left threaded upon the cable guide tube 50, as desired. A bushing 74 may be inserted in the upper end of the tube 50 in any case wherein the diameter of the cable is substantially less than the inner diameter of the tube 50. When such a bushing is used the inner diameter thereof is such as to afford a reasonably snug fit upon the cable and the outer diameter is such as to make a friction fit inside the upper end of the cable guide tube 50. A similar bushing 76 may be provided for the cable guide tube 52 as shown in FIG. 2. The tube 50, with or without the bushing 74 is then strung upon the cable 14 after which the cup 46 is strung on the cable. The cup 46 is provided with an opening 78 to receive the cable and the diameter of said opening 78 preferably is appropriate for the largest size cable expected to be used. When, as shown in FIG. 4, the diameter of the cable 14 is substantially less than that of the opening 78 a washer 80 is next strung upon the cable 14. The washer 80 has an inner diameter such as to rather snugly fit upon the cable 14 and an outer diameter such as to be readily received but quite accurately centered in the cup 46. A similar washer 82 may be provided for the cup 48 as shown in FIG. 2

If the cable end is to be secured in the cup 46- by babbitting the guide tube 50 is preferably moved up the cable for a distance suitable to protect it from heat or fouling incident to the babbitting operation. The end of the cable portion 14 is then splayed out, as is customary, and the splayed end 84 is seated against the washer 80 within the cup 46. Babbitt metal 86 is then poured into the cup and is permitted to cool. Corresponding parts are then assembled and secured upon the other cable portion 12 in the same manner as just described. The splayed end of cable portion 12 is indicated at 88 in FIG. 2 and the babbitt metal is indicated at 90.

Instead of babbitt, it may be desired to utilize a cable clamp upon the ends of the cable portions 12, 14. If so, it is preferable, if clamps of such size as to fit within the cups 46 and 48 are unobtainable or impractical, to provide rigid tubes (not shown) slipped over the cable ends to bear on the upper walls of the cups 46 and 48 and to extend downwardly beyond the cups to receive upward thrust exerted by cable clamps which may be too large to enter the cups.

The bridle cable with the attached parts is next secured to the horsehead so that the tubes 50 and 52 and other parts assembled upon the cable ends will hang adjacent the polish rod as shown in dotted lines in FIG. 2. The shock absorber assembly including the base member 20 and load supporting member 22 is then placed over the polish rod 16. A pressure plate 92 having an inner diameter appropriate for the particular diameter of polish rod 16 is then placed over the upper end of the rod and dropped into position. The pressure plate 92 is provided with a shoulder 94 which fits snugly within a central opening 96 formed in the load carrying member 22. In this manner the polish rod is accurately and permanently centered with respect to the body of the shock absorber of the present invention. If so desired the pressure plate 92 may be made up of two or more segments so that it may be assembled around the polish rod 16 to avoid the need for slipping it over the upper end of the rod.

The polish rod clamp 18 is next put into position and secured to the rod 16 whereby lifting of the shock absorber will be effective to lift the polish rod and attached pump rod string.

The cable ends with the detachable parts secured thereto may now be swung inwardly, inserted in the side openings 38, 4t 66, 68 of the shock absorber and secured in place by tightening of the clamp nuts 6-2, 64 and lock nuts 70, 72 as described above. The installation is now complete. It will be appreciated that such installation does not require pulling of the well and that during the installation as described above there is no period wherein any heavy parts are dangling from the ends of the bridle cable. The shock absorber assembly may weigh several hundred pounds and would be difficult to attach directly to the swinging ends of the bridle cable. Furthermore, it could be dangerous and at least would be difficult to position upon the polish rod if it were to be first hung from the bridle cable. It will be appreciated that after the initial installation the bridle cable with the attaching parts secured thereto may be quickly disengaged from and re- 6 engaged with the base plate 20 whenever servicing of the well may be required. Similarly the heavy parts 20, 22 with the associated spring and cushion members 28, 32 may be removed and replaced as a unit when servicing of the well is required.

To hold the shock absorber together during shipment and installation it is preferred to provide tension rods 98 and 100 (see FIG. 1) which extends through and between the base 20 and load supporting member 22. As shown in FIG. 2, the tension rod 100 may be provided with locking nuts 102 at both ends thereof to hold it in position. Similar nuts 184 are provided for the rod 98. The tension rods 98 and may be left in place while the shock absorber is in use and thus will be available to hold the device together in the event it is removed from the well. Preferably the tension rods 98 and 100 make a loose fit in openings (not numbered) in the base 20 and load-carrying member 22 whereby they will not interfere with or be damaged by the relative movements which occur between the base and load-carrying member during the pumping operation. Preferably, also, the length of the tension rods 98 and 100 is such as to hold the shock absorber, when in the unloaded condition illustrated in FIG. 2, under a very small amount of precompression, suflicient, for example, only to prevent the parts from rattling or becoming disassembled during shipment or other periods of non-use. With tension rods 98 and 180 of such length negative loadings, that is any loadings which would tend to lift the load-carrying member 22 further away from the base 28 than it is in unloaded condition normally will not be encountered in pumping operations but if they are the tension members 98 and 100 will serve to hold the parts in assembled position.

It will be apparent that the shock absorber of the present invention could be placed under substantial precompression, perhaps rather closely approaching the amount of compression which will occur when the static load of pump rod string is suspended from the load carrying member 22. No particular advantage is believed to be afforded by any such precompression but if it is practiced the tension rods 98 and 188 or other mechanical equivalent thereof must be so designed as to withstand not only the static loading due to precompression but also such rebound shock loading as is likely to occur at the top of each pumping stroke or upon sudden reductions in loading resulting, for example, from breaking of the pump rod string.

The cable guide tubes 50 and 52 are shown in FIG. 2 as extending upwardly substantially to the level of the top surface of the load-supporting member 22. Since FIG. 2 shows the shock absorber in unloaded position it will be appreciated that when the static load consisting of the pump rod string is placed upon the load-supporting member 22 the latter will be moved downwardly toward the base member 20. Strictly speaking, the cable guide tubes 50 and 52 need only to extend upwardly to approximately the level assumed by the load-supporting member 22 under such static load in order to minimize tilting and consequent bending stress upon the polish rod 16 during the pumping operation. The extra length of the tubes 50 and 52 as well as the additional length that may be contributed by the bushings 76, if used, does no harm and as a practical matter makes it possible to use a shock absorber unit of particular size with pump rod strings of widely different lengths and weights.

As noted above the active shock-absorbing and load carrying elements of the present invention are the springs 28 and the metal cushions 32 positioned within the springs. The cushions 32 preferably are cylindrical and fit rather snugly within the inner diameter of the springs 28 and also preferably are substantially coextensive in axial length with the springs. In such preferred relationship the cushions 32 will serve continuously to support a portion of the load and will serve to damp movements of the spring in both compressive and expansive directions. If desired, however the cushions 32 may fit rather loosely in the springs 28 or they may be somewhat shorter than the springs 28 or both. In any of the latter cases the cushions will be effective to damp at least a portion of the compressive movements of the springs and when they are shorter than the springs they will be effective to support a portion of the heavier loads. The combined spring and cushion units herein provided are vastly superior to rubber cushions, for example, in the present use. Much greater deflection can be provided for on each stroke and the damping of shock pulses is far more effective than can be the case when rubber cushions of the size and density required for such heavy loadings are used. Furthermore the all-metal construction is superior in respect of withstanding extremes of temperature, chemical attack and the like.

The cushions 32 preferably are compressed masses of metal wire in which innumerable short spans of wire cross one another so as to form delicate springs which will yield readily for small deflections but which, in total, offer rapidly increasing resistance to deflections of increasing amplitude. Such cushions may be made up for example by knitting a metal fabric tube from metal wire and flattening and rolling up such a tube to form a cylindrical mass. The cylindrical mass is then compressed under sufficient pressure to overcome the elastic limit of the wire at innumerable points whereby the finished compressed cylinder is of the desired size and degree of firmness. One particular advantage of cushions so fabricated is that although each length of wire is bent locally in many random directions there is a generally uniform orientation of the overall lengths of wire in directions generally parallel with the cylindrical axis of the cushion. These oriented wires thus become a mass of individual springs each extending from end to end of the cushion and each interlocked with adjacent springs to impart to the cushion its high degree of damping and its long life under cyclically repeated loadings. By associating metal spring cushions of this type with ordinary coil springs which have characteristics so different from those of the cushions a combined effect of yieldability, nonlinear spring rate and highly effective damping is achieved. These combinations have been found to be highly effective in coping with the particular conditions encountered in the pumping of deep wells and it has been possible to sharply increase the pumping rate at operating wells and at the same time to sharply decrease the frequency of pump rod breakage.

In instances wherein damping is not regarded as essential the cushions 32 may be omitted and the springs 28 thus will be relied upon alone to absorb the shock and vibratory loads encountered. In other instances the damping characteristics and spring rates offered by certain elastomeric materials may be desired. Thus, natural rubber cushions with or without the surrounding coil springs 28 herein disclosed may be used, particularly in the absence of petroleum, ozone or other substances destructive of natural rubber. Synthetic elastomeric materials may be used in suitable environments and many of them afford damping characteristics superior to natural rubber. For example, polyurethane either solid or in foam form may be used for cushions with or without the surrounding coil springs 28. Good damping is afforded by cushions of polyurethane foam with a system of open pores. The words spring means as used in certain of the claims are intended to include any of the cushions or cushion and spring combinations of the types herein disclosed as well as springs without cushions.

In any of such modifications or adaptations of the present invention the advantages of rapid and convenient assembly and disassembly of the shock absorbing device with the pump rod string and the pumping device together with the minimizing of lateral or bending stresses upon the pump rod will be realized as they have been described herein in connection with the preferred form of the invention.

I claim:

1. In a shock absorbing coupling for connection between a pumping mechanism including a plurality of lengths of vertically depending flexible cable which are cyclically lifted and lowered in a pumping operation, and a pump rod string including a length of rod extending vertically from a well head, the combination of a rigid base member having a passageway therethrough for the free passage of the length of rod; a rigid load-supporting member positioned above said base member; means for attaching the length of rod extending through said base member to said load-supporting member; spring means extending vertically between said base member and said load-supporting member to support said load-supporting member and the rod string for yielding movement relative to said base member in response to forces applied to said base member for lifting said rod string and in response to shock and vibratory loads incident to a pumping operation; and means for attaching each of said lengths of flexible cable to said base member, said last named means each comprising a cable-engaging member attached to the lower end of said cable, a rigid metal tube enclosing said cable and extending vertically above said cable engaging member for a distance at least approximately equal to the distance between said base member and said load-supporting member under the static load of said rod string, and means for rigidly securing said metal tube to said base member whereby during pumping operation said cable is prevented from flexing relative to said base member at any point between said load-supporting member and said base member.

2. A shock absorbing coupling in accordance with claim 1 in which each of said cable-engaging members is an inverted metal cup in which the end of said cable is secured by babbitting and upon which said metal tube is adapted to rest during pumping operation.

3. A shock absorbing coupling in accordance with claim 1 in which said base member and said load-supporting member are provided with vertically aligned openings extending inwardly from the edges thereof to receive by lateral movement thereinto said metal tube with the cable positioned therein preparatory to the securing of said tube to said base member.

4. A shock absorbing coupling in accordance with claim 2 in which said base member and said load-supporting member are provided with vertically aligned openings extending inwardly from the edges thereof to receive by lateral movement thereinto said metal tube with the cable positioned therein preparatory to the securing of said tube to said base member.

5. A shock absorbing coupling in accordance with claim 1 in which said spring means comprises a plurality of compressible coil springs and a plurality of yieldable cushions arranged in substantial symmetry around the axis of said length of rod, said cushions providing damping of said yielding movement between said load-supporting member and said base member.

6. A shock absorbing coupling in accordance with claim 2 in which said spring means comprises a plurality of compressible coil springs and a plurality of yieldable cushions arranged in substantial symmetry around the axis of said length of rod, said cushions providing damping of said yielding movement between said load-supporting member and said base member.

7. A shock absorbing coupling in accordance with claim 3 in which said spring means comprises a plurality of compressible coil springs and a plurality of yieldable cushions arranged in substantial symmetry around the axis of said length of rod, said cushions providing damping of said yielding movement between said load-supporting member and said base member.

8. A shock absorbing coupling in accordance with claim 4 in which said spring means comprises a plurality of compressible coil springs and a plurality of yieldable cushions arranged in substantial symmetry around the axis of said length of rod, said cushions providing damping of said yielding movement between said load-supporting member and said base member.

9. A shock absorbing coupling in accordance with claim 5 in which said cushions comprise compressed masses of metal wire.

10. A shock absorber in accordance with claim 6 in which said cushions comprise compressed masses of metal wire.

11. A shock absorber in accordance with claim 7 in which said cushions comprise compressed masses of metal wire.

12.. A shock absorber in accordance with claim 6 in which said cushions comprise compressed masses of metal wire.

13. A shock absorbing coupling in accordance with claim 1 wherein said means for securing said metal tube to said base member includes a screw thread on the exterior surface of said metal tube, a flange secured to and extending radially of said tube near the lower end thereof and adapted to bear upwardly upon a portion of the lower surface of said base member adjacent the tube-receiving opening therein, and a clamp not adapted to be fitted upon said screw thread and screwed downwardly into engagement with a portion of the upper surface of said base member.

14. A shock absorbing coupling in accordance with claim 3 wherein said means for securing said metal tube to said base member includes a screw thread on the exterior surface of said metal tube, a flange secured to and extending radially outwardly of said tube near the lower end thereof and adapted to bear upwardly upon a portion of the lower surface of said base member adjacent the tube-receiving opening therein, and a clamp nut adapted to be fitted upon said screw thread and screwed downwardly into engagement with a portion of the upper surface of said base member.

No references cited.

ARTHUR L. LA POINT, Primary Examiner.

R. M. WOHLFARTH, Assistant Examiner. 

1. IN A SHOCK ABSORBING COUPLING FOR CONNECTION BETWEEN A PUMPING MECHANISM INCLUDING A PLURALITY OF LENGTHS OF VERTICALLY DEPENDING FLEXIBLE CABLE WHICH ARE CYCLICALLY LIFTED AND LOWERED IN A PUMPING OPERATION, AND A PUMP ROD STRING INCLUDING A LENGTH OF ROD EXTENDING VERTICALLY FROM A WELL HEAD, THE COMBINATION OF A RIGID BASE MEMBER HAVING A PASSAGEWAY THERETHROUGH FOR THE FREE PASSAGE OF THE LENGTH OF ROD; A RIGID LOAD-SUPPORTING MEMBER POSITIONED ABOVE SAID BASE MEMBER; MEANS FOR ATTACHING THE LENGTH OF ROD EXTENDING THROUGH SAID BASE MEMBER TO SAID LOAD-SUPPORTING MEMBER; SPRING MEANS EXTENDING VERTICALLY BETWEEN SAID BASE MEMBER AND SAID LOAD-SUPPORTING MEMBER TO SUPPORT SAID LOAD-SUPPORTING MEMBER AND THE ROD STRING FOR YIELDING MOVEMENT RELATIVE TO SAID BASE MEMBER IN RESPONSE TO FORCES APPLIED TO SAID BASE MEMBER FOR LIFTING SAID ROD STRING AND IN 